In recent years, in manufacturing a semiconductor device, a non-plasma dry etching technique called a chemical oxide removal (COR) has been focused as a miniaturization etching technique substituted for a dry etching or a wet etching. Only a hydrogen fluoride (HF) gas or a mixed gas of the HF gas and an ammonia (NH3) gas has been used in etching an oxide such as a silicon oxide (SiO2).
The COR technique is used to etch the oxide such as the silicon oxide (SiO2), but in recent years, is under consideration as a way to etch a portion of silicon (Si) contained in a polysilicon (poly-Si) film or the like. The polysilicon film, together with other films such as a silicon nitride (SiN) film, is formed on a semiconductor wafer (or a silicon wafer) used as a substrate to be processed. As such, the polysilicon film is required to be etched at a high etching selectivity compared to the SiN film or the like. From such a point of view, a mixed gas of HF gas+F2 gas is under consideration as a gas for etching the portion of silicon (Si) using the non-plasma dry etching technique.
However, etching the portion of silicon (Si) using the mixed gas of HF gas+F2 gas results in a considerable reduction in etching rate, which makes it difficult to employ as a mass production technology.